Over the history of digital computers there has been a continuous trend toward higher performance. Recent advances in integrated circuit (IC) manufacturing technology have produced smaller and faster ICs such that current microprocessor-based computer systems have higher performance that supercomputers of a generation ago. Microprocessor performance is determined by many factors, including clock speed and data bus width.
Typically IC manufacturers have been able to offer higher speed versions of a particular microprocessor over its lifetime. The continual improvement in microprocessor speed has created the opportunity for users to upgrade their computer systems with newer, higher speed microprocessors. Thus an older, slower microprocessor could be unplugged from its socket and a new, higher speed microprocessor inserted in its place. An example of this type of upgradeability is a microprocessor that can communicate with a memory device at one speed but whose internal clock speed can be scaled to a higher frequency, as disclosed in U.S. Pat. No. 5,828,869 to Johnson et al.
This type of upgrading has allowed significant performance increases in single processor systems. However recent computer architectures have become more complex than single processor systems. For example some computer architectures now use multiple processors and non-uniform memory accessing (NUMA). In such NUMA systems, two or more microprocessors are connected in a ring or network and each have associated memory and possibly one or more associated input/output devices. It would be desirable for users to begin with a low-cost NUMA system and upgrade the system to improve performance later.
Accordingly, it would be desirable to provide a new means of upgrading performance in multiprocessor computer systems. This and other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.